The present invention is directed to a coating composed of an optically effective layer system, for substrates, whereby the layer system has a high anti-reflective effect. The invention is also directed to a method of manufacturing the layer system.
There is a wide range of layer systems for substrates, particularly for glass, which fulfill certain optical functions.
German OS 36 29 996 discloses an adaptor unit/aggregate for cathode ray tubes of monitors, television sets and such, which unit is composed of a glass disk, particularly a gray glass disk, with a front side anti-reflection equipment and a backside absorption coating. The absorption coating comprises metal atoms. In this German publication it is suggested that the absorption coating is structured in a one-layered fashion from chromium, a chromium/nickel - alloy or silicides, and established and grounded antistatically, as well as provided with a thickness which lowers the light transmission compared to the uncoated glass disk by approximately one third.
U.S. Pat. No. 3,854,796, whose disclosure is incorporated herein by reference thereto, discloses a coating for the reduction of reflection. The coating is to be applied on a substrate and has a plurality of layers. In the sequence beginning at the substrate, the U.S. patent describes the following arrangement: three groups of at least two lambda/4-layers, the successive layers of the first group have a refractive index lying below the refractive index of the substrate. The layers of the second group have an increasing refractive index and the layers of the third group have a refractive index decreasing below that of the substrate.
U.S. Pat. No. 3,761,160, whose disclosure is incorporated herein by reference thereto, discloses a broadband-anti-reflection-coating and substrates which are coated with such a coating. The coatings have at least four layers for glass with a high index of refraction and at least six layers for glass with a low index of refraction.
U.S. Pat. No. 3,695,910, whose disclosure is incorporated herein by reference thereto, describes a method for the application of a anti-reflective coating on a substrate. This coating is composed of several individual layers. The method for the application of the anti-reflection coatings occurs under vacuum, namely with the use of electron beams.
U.S. Pat. No. 3,829,197, whose disclosure is incorporated herein by reference thereto, describes a anti-reflection coating fashioned as a multi-layer system. This coating is to be applied on a highly refractive substrate. The layer system is composed of five individual layers which are mutually adapted namely regarding their refractive index and regarding their optical thickness. This adaptation is to achieve a favorable anti-reflection curve with a broad, flat, center part.
Swiss Patent No. 223344 also belongs to prior art. This patent deals with a coating for the reduction of surface reflection. The coating is composed of at least three layers with various refraction coefficients. The reduction of the surface reflection shall be achieved according to this reference by a certain selection of refraction coefficients of the individual layers.